During World War I he served from August 1914 to October 1918 in the Austro-Hungarian army in the 1st Regiment of Uhlans of National Defence, fighting on the French, Romanian, Russian, Serbian and Italian fronts, ending his service as a Lieutenant in the cavalry.

From 1 November 1918 in the reformed Polish Army in the rank of lieutenant, he was the commander of the Góra Strudenia sector in Lwów.

An account, for instance, cited that the Galician unit he commanded allegedly plundered from peasants living in captured Ukrainian villages, hauling all that could be transported to Lwów.

[1] From January to August 1919 he commanded an independent battalion, regiment and Operational Group in the division of Colonel Władysław Sikorski.

He was wounded during the conflict but he continued performing his duties, commanding his unit whilst being carried on a stretcher.

A handwritten card sent by Abraham to his friend in Chicago from his prison has been preserved, and is currently part of the Centralne Muzeum Jeńców Wojennych's collection.